The monoclonal immunoglobulin (Ig)M from 5 to 16 patients with Waldenström's macroglobulinemia and a polyneuropathy shared cross-idiotypic antigenic determinants as demonstrated by hemagglutination and hemagglutination inhibition experiments as well as by precipitin reactions. This reactivity was located to the Fab (and not Fc) fragment of the protein. The IgM from 73 patients with macroglobulinemia but without neuropathy all gave negative reactions. In contrast, the monoclonal IgG from a patient with polyneuropathy also possessed similar idiotypic determinants. Since cross-idiotypic determinants are usually related to the combining site of a monoclonal Ig, this finding suggests that the monoclonal Ig of these patients may mediate the nerve injury via their antibody activity, which could be directed either to a nerve antigen or to some component involved in the pathogenesis of the neuropathy.
K Dellagi, J C Brouet, F Danon